"Police will allege the baby, believed to have been born on Monday [17 November] was placed into the drain on Tuesday," a police statement said.

Andrew Pesce, a gynaecologist, obstetrician and former president of the Australian Medical Association, said such an ordeal could leave a newborn with long-term problems such as brain damage.

"There would still have to be some concerns about the baby," Pesce said.

"I would have thought that it wouldn't have been able to survive for much longer if it didn't start getting fed," he added.

He said healthy newborns have reserves to cope with relative malnutrition and often lose 10 percent of their birth weight because their mothers can take a few days before producing sufficient milk.

The baby had been squeezed into this drain from where he dropped a distance of 8ft

Helen Polley, a senator in the opposition Labor Party, said the near-tragedy could have been avoided if emergency hatches were rolled out at Australian hospitals, police and fire stations where babies could be safely abandoned.

She called for the repeal of laws that make child abandonment a criminal offense, which she said encourage the problem to be hidden.

Cyclists riding along a bicycle lane beside the motorway heard the baby on Sunday morning.

"We actually thought it was a kitten at first, but when we went down there we could hear exactly what it was — you could definitely tell it was a baby screaming," cyclist David Otte told The Daily Telegraph newspaper.

It took six men, including three police officers, to lift the 200kg concrete lid that covered the drain, the newspaper said.

Police suspect the baby was squeezed through the drain's narrow opening and dropped to the bottom.

Hewas found wrapped in a hospital blanket, and police used hospital records to find the mother.

The baby is likely to be taken into state care when he is discharged from the hospital, officials said.